Technical Field
The present disclosure is related to an unlicensed spectrum communication scheme applied in the wireless communication system, and more particular to a method and device for communication on an unlicensed spectrum based on long term evolution (LTE).
Related Art
In the traditional LTE system of the 3rd Generation Partner Project (3GPP), data transmission only occurs on the licensed spectrum; however, with the sharp increase in the business volume, especially in some urban areas, the licensed spectrum may be difficult to meet the demand of the business volume. The sixth-second plenary of 3GPP RAN discusses a new research topic, i.e. the comprehensive research of the unlicensed spectrum (RP-132085). The main purpose is to research the non-standalone deployment of LTE on the unlicensed spectrum, wherein the so-called non-standalone means that the communication on the unlicensed spectrum is required to be associated with the service cell on the licensed spectrum. An intuitive approach is to reuse the carrier aggregation (CA) in existing system as far as possible, i.e. the service cell deployed on the licensed spectrum serves as the primary component carrier (PCC), and the service cell deployed on the unlicensed spectrum serves as the secondary component carrier (SCC).
In the traditional carrier aggregation, a user equipment (UE) is capable of being configured with the maximum of five downlink carriers at the same time, and on the maximum of five downlink carriers, the physical downlink shared channel (PDSCH) is simultaneously received and on the physical uplink control channel (PUCCH) of PCC, the hybrid automatic repeat request (HARQ) acknowledgement (HARQ_ACK) of the PDSCH on the downlink carrier is feedbacked. The feedbacked HARQ_ACK may use the PUCCH format 1b or the PUCCH format 3, wherein the format 1b combined with a channel selection technique is applied for a scene including two carrier and the HARQ_ACK bits not greater than 4, and the format 3 is capable of supporting the maximum of twenty HARQ_ACK bits.
For the unlicensed spectrum, considering the non-controllable/predictable of the interference level thereof, the UE may be configured with more downlink carriers, and simultaneously uses a manner of dynamical frequency selection (DFS) to select a part of downlink carriers from the configured downlink carriers (in a given sub frame) for the PDSCH transmission. Further, considering the bandwidth of the unlicensed spectrum is larger, for example an unlicensed spectrum with about 500 MHz is available near the carrier frequency of 5 GHz, the carrier number configured by the UE may be larger (much larger than five). The traditional PUCCH format 3 may not support all configured carrier feedback HARQ_ACK. Additionally, after using DFS, it may lead to the frequent discontinuous transmission on the same physical carrier, thereby increasing the interval of the HARQ re-transmission and increasing the transmission delay.
For the above problems, the present disclosure discloses a method and device for communication on an unlicensed spectrum.